Effect of fluoride exposure on bone metabolism indicators ALP, BALP, and BGP

To analyze the changes in serum alkaline phosphatase (ALP) and bone alkaline phosphatase (BALP) activity and changes in osteocalcin (BGP) content following fluoride exposure and, thereby, determine the reference indications of fluoride-induced changes in bone metabolism.

In the animal study, rats were allowed free access to drinking water containing different concentrations (10, 150, or 400 mg/L) of sodium fluoride. Serum ALP and BALP activity and serum BGP content were assessed at three exposure time-points. In the spot study, serum ALP and BALP activity and serum BGP content were assessed in workers exposed to fluoride in their working environment for different periods of time.

Compared with the control group, on days 15 and 30, the activity of serum ALP in the low- and medium-dose group was significantly higher (p < 0.05), while in the high-dose group it was significantly lower (p < 0.05). Only on day 30 was the activity of serum BALP in the medium-dose group significantly higher than that of the control group (p < 0.05). BGP content was lower in the high-dose group than in the control group (p < 0.05) on days 30 and 90, but it was higher in the medium-dose group on day 90. Compared with the control group, BGP content in the fluoride-exposed group was higher (p < 0.05). In the spot study, serum ALP activity and serum BGP content in the medium working-age group were higher than that in the short working-age group (p < 0.05). However, serum ALP activity and serum BGP content were lower in the long working-age group than in the medium working-age group (p < 0.05).

Our results suggest that serum fluoride and urinary fluoride can be used as reference indications to provide an overall reflection of the body's fluoride-load and fluoride exposure level. Serum ALP activity and serum BGP content can be used as important reference indications for diagnosing bone metabolism changes resulting from fluoride exposure.